Sensitive control instrument



June 22, 1937. P. w. CUMMINGS SENSITIVE CONTROL INSTRUMENT OriginalFiled Dec. 15, 1930 4 INVENTOR Pr eYston WGummm s {flaw/M64,

ATTORN EYS Patented June 22, 1937 SENSITIVE CONTROL INSTRUMENT PrestonW. Cummings, Rockford, Ill., assignor to Howard D. Colman, Rockford,Ill.

Application December 15, 1930, Serial No. 502,379 Renewed November 14,1936 17 Claims.

The invention relates to sensitive control instruments such asthermostats and hygrostats, and has particular reference to thermostatsof the type known in the art as insertion thermostats and commonlyemployed in the control of a primary heat source to avoid overheating.

One of the objects of the invention is to provide in a thermostat of thecharacter indicated, a combined supporting and adjusting means for thesensitive actuating element which means is of an advantageous character,both from the manufacturing and operating standpoint.

Controlling instruments of the general character first above referred tocommonly include a control device having a movable switch member in theform of a tongue mounted for swinging movement relative to one or morestationary switch contacts, and actuated by a sensitive elementresponsive to varying temperature or humidity conditions of thesurrounding medium. vAn important object of my invention is to providean improved motion-transmitting connection between the movable memberand the sensitive actuating element, which is adapted to prevent injuryto the parts in the event that the actuating element, responding towidely varying conditions in the surrounding medium, attempts to impartto the movable member a greater range of movement than is permitted bythe arrangement of the stationary member or mem bers.

A further object is to provide an improved mounting for the movablemember or tongue so as to enable an easy and convenient cleaning ofopposed stationary switch contacts.

The objects of the invention thus generally stated, together with otherand ancillary advantages, are attained by the construction andarrangement shown in the accompanying drawing wherein my invention isillustrated in connection with an electric thermostat. In the drawing:

Figure 1 is a front elevational view of the improved thermostat with asubstantial portion of the front cover broken away to illustrate theconstruction and arrangement employed.

Fig. 2 is a fragmentary sectional View taken approximately in the planeof line 2-2 of Fig. 1 and showing the thermostat applied to a boiler.

In the selected embodiment of the invention as illustrated, the controlinstrument comprises, in general, a somewhat elongated substantiallyrectangular casing 3 in the lower portion of which is mounted a controldevice of the electrical type. The latter device comprises a pair ofstationary switch contacts 4 and 5 spaced apart in cooperative relationwith an intermediate tongue 6 constituting a movable contact membercommon to both of the stationary contacts 4 and 5. The tongue 6 ismounted approximately centrally of the casing on a shaft I which extendsrearwardly from the casing through a tube 8 of substantial lengthjournaled in the casing. A sensitive actuating element 9 in the form ofa helically coiled bimetallic strip has its opposite ends securedrespectively to the shaft 1 and the tube 8, and operatively associatedwith the tube and disposed within the casing largely within the upperportion thereof is a manually operable setting means generallydesignated by the numeral I 0.

The casing 3 may be made of any suitable material, metallic ornon-metallic. It comprises a rear section or base H and a front or coversection l2, the latter being removable to permit of convenient access tothe interior of the casing when desired. The base is provided with acentral aperture defined at its rear edge by an annular flange l3. Thisflange is mounted to turn relative to the forward end of a tubularhousing I4 enclosing the shaft "I, tube 8 and thermostatic element 9.The tubular housing H in turn is pressed into a threaded bushing I 5adapted to be secured into a suitable aperture of one wall of a boileror the like as indicated at 16. The bushing It has at its outer orforward end a head I! to which the base section H of the easing issecured by means of screws I8 entered through slots IS in the basesection. The head i! may be provided with a plurality of tapped holes 20(Fig. l) which, together with the slots l9, permit the casing to besecured in upright position irrespective of the extent to which thebushing may be threaded into the boiler Hi.

The stationary switch contacts 4 and 5 may be of any suitable orpreferred character. Herein they are shown mounted upon the base II insuitably spaced relation for coaction with the tongue 6 whichconstitutes the movable contact member common to both of the stationarycontacts 4 and 5. 2i designates a binding post which is connected to thetongue by means of a conductor 22, and the contacts 4 and 5 areconnected to binding posts 23 and 24 respectively.

The shaft 1, in accordance with the present construction, has asupporting bearing only at its forward end. This bearing is provided inthe present construction by the lower end of an arm 25 which is fast tothe forward end of the tube 8 as by being pressed thereon, the journalbearing for the shaft being formed by an aperture 28 in the arm. Thetube 8 in turn is mounted for rotative adjustment in a bearing sleeve 21which is pressed into the central aperture in the base H and extendsrearwardly a short distance into the tubular housing M. The sleeve 21 ispreferably in the form of a tube of a diameter somewhat larger than thatof the tube 8 but having its opposite ends turn inwardly as at 28 toform spaced bearings for the tube 8.

The connection between one end of the thermostatic element 9 and theshaft 1 is effected by means of a nut 29 screw threaded on the rear endof the shaft which extends through the coiled element. The opposite endof the element is secured to the tube 8 through the medium of a collar30 fixed on the tube and having a flange 3| fitting loosely within thetubular housing l4.

A coiled expansion spring 32 encircling the tube 8, bears between therear end of the bearing sleeve 21 and the collar 30 so as to hold thearm 25 at the forward end of the tube flat against the forward end ofthe bearing sleeve 21, and against an annular forwardly projectingflange 33 on the base section I I, which flange terminates flush withthe forward end of the bearing sleeve. The spring thus serves to holdthe tube 8 in position within the tubular housing l4, while the flange3! on the collar 30 positively prevents any contact between thethermostatic element 9 and the housing. Thus it will be observed thatthe tube 8 is supported at the opposite ends of the sleeve 21, whereasthe shaft 1 has a bearing only in the arm 25. Because the diameter ofthe shaft is small, very little frictional resistance is offered by thebearing to the rotation of the shaft by the thermostatic element 9; andsince the bearing is short, accurate alinement of the shaft relativethereto is rendered unnecessary.

The arm 25 constitutes a part of the adjusting means, and has for thispurpose its upper end operatively connected to a hand-operated settinglever 34. This lever is pivoted at 34 to the base section II, at a pointbelow the upper end of the arm 25, and the upper end of the settinglever 34 is bent so as to extend forwardly through a slot 35 in thecover section 12. The forward end of the arm 34 may be provided with apointer 36 to cooperate with a scale 31 to enable the thermostat to beadjusted for any desired temperature.

The connection between the upper end of the arm 25 and the setting lever34 may be of the pin-and-slot type, including an eccentricaliy mountedadjustable stud 38 on the lever bearing in a slot 39 formed in the upperend of the arm. The stud 38 is capable of individual adjustment for thepurpose of adjusting the relation between the tongue 6 and the settinglever 34. For the purpose of retaining the setting lever in its adjustedposition, the latter is provided with a laterally enlarged portion 40having an arcuate slot 4| therein (Fig. 1) through which a screw 42 isentered, which screw is anchored in the base section H and carries acoiled spring 43 interposed between the head of the screw and. a washer44 bearing against the front side of the setting lever 34.

The motion-transmitting connection between the tongue 6 and the shaft 1is of a yieldable character to avoid injury to the parts in the event ofan excessive movement imparted to the tongue by the thermostatic elementover and above that permitted by the spacing of the stationary con tacts4 and 5. This connection comprises in the present instance a block 45anchored to the forward end of the shaft 1 through the medium of aninsulating bushing 46 and a screw 41. The screw is made of substantiallength so as to project radially from the block 45 and is enteredthrough an aperture in a rearwardly bent portion 48 of the tongue 6.Such apertured portion of the tongue rests upon the upper side of theblock 45, and a spring 49 bearing between the head of the screw and awasher 50 tends to hold the anchoring portion of the tongue againstrotation relative to the shaft. Thus the parts 45 and 48 providecoacting positioning surfaces normally held in engagement by the spring49 to define a normal predetermined relation between said parts, theconstruction being such that the spring yieldably holds the partsagainst relative movement in either direction out of such normalrelation. It will be apparent however that the spring 49 is capable ofyielding to permit relative movement between the shaft and the tongue inthe event that the shaft is turned beyond its normal range of operationin either direction with the tongue limited in its movement by either ofthe contacts 4 and 5. To assist in fastening the block 45 on the shaft,the latter may be knurled as indicated at 5| to receive the insulatingbushing 46 in tightly fitting or interengaging relation.

To prevent contact between the block 45 and the arm 25, in the event ofrearward axial movement of the shaft, an insulating washer 52 isinserted between the block and am.

It will be apparent that when it is desired to change the setting of thethermostat, this may be accomplished readily through the manipulation ofthe setting lever 34 which operates through its connection with the arm25 to rotate the adjusting tube 8 connected with one end of thethermostatic element 9. The other end of the element being connected tothe tongue 6 effects the desired adjustment. It will also be observedthat the thermostat as constructed is adapted to correspond reliably tochanges in the heating medium to which it is subjected, the onlyfrictional resistance to rotation of the shaft and hence movement of thetongue by the thermostatic element being supplied by the relativelyshort bearing 26. If the movements imparted to the tongue by thethermostat are excessive, injury to the parts is avoided by the yieldingof the spring 49.

The assembly comprising the thermostatic element, the supporting tube 8,operating shaft 1 and adjusting arm 25, is effectually held in operativeposition by the spring 32 coacting with the bearing sleeve 21. Theconstruction furthermore provides for the convenient cleaning of theswitch contacts by the removal of the cover section ll of the casing. Todo this, it is only necessary to grasp the block 45 carrying the tongue6, and draw the shaft 1 and tube 8 forwardly against the action of thespring 32, the tube in this operation sliding forwardly in the bearingsleeve 21 and the arm 25 moving forwardly correspondingly out ofengagement with the eccentric stud 38. By such an operation, the tongue6 may be moved out of position with the contacts 4 and 5 thus renderingit possible readily to clean these con tacts.

In general, the construction provided is of a practical character,capable because of its simplicity, of being manufactured at a low cost.Also, the device is capable of convenient adjustment, its switchcontacts may be easily cleaned or repaired, and certainty and accuracyof operation is insured.

I claim as my invention:

1. A thermostat comprising a helically coiled thermostatic element, asupport for one end of said element, a shaft to which the other end ofsaid element is secured, a movable switch contact mounted on the shaft,a stationary switch contact, and means for supporting said shaft adaptedto permit axial movement, and spring means normally holding the shaft inposition to maintain said contacts in operative relation.

2. A thermostat comprising, in combination, a tubular member, a supportfor one end of said member adapted to permit of the rotative. adjustmentof the latter, a shaft extending through said tubular member with itsopposite ends projecting therefrom, a helically coiled bimetallicelement having its opposite ends fixed respectively to said shaft andsaid tubular member, means including a spring acting upon said tubularmember to hold it in position in the support, and a switch membermounted on said shaft adjacent the support.

3. A thermostat of the character set forth comprising a shaft, ahelically coiled thermostatic element fixed to one end of said shaft, anadjustable support for the opposite end of said thermostatic element, abearing in which the opposite end of the shaft is slidably supported, aswitch member mounted on said shaft and movable by said thermostaticelement, a pair of stationary contacts on opposite sides of said switchmember,

and spring means normally acting to hold said shaft in position withsaid switch member disposed between said contacts, said spring meanspermitting an axial movement of'the shaft to remove the movable switchmember from position between said contacts.

4. A thermostat comprising a base, a shaft having one end rotatably andslidably mounted in said base, a temperature-responsive element forrotating said shaft, a support for said element mounted for movementwith the shaft when the latter is slid endwise relative to the base,means for adjusting said support including an arm fixed thereto and alever pivoted to the base and having a pivotal connection with said arm,a pair of stationary switch contacts, and a movable switch contactmounted on the shaft and normally disposed between the stationarycontacts, said shaft being manually slidable endwise in said base topermit the movement of the movable switch contact out of operativerelation to the stationary contacts, and said pivotal connection beingadapted to permit disengagement of said arm from the lever in themovement of the support with the shaft.

, 5. A thermostat having, in combination, a base,

an elongated tube, a bearing sleeve mounted in said base and having saidtube rotatively adjustable therein, a member fixed to said tube adjacentsaid sleeve, a shaft having one end mounted in said member and its otherend projecting from the opposite end of the tube, a helically coiledthermostatic element having its ends fixed respectively to said shaftand to said tube, and a spring acting between said tube and said bearingsleeve to hold the tube in position in said base.

6. A thermostat having, in combination, a support, an elongated tubehaving one end rotatively mounted in said support, a shaft extendingthrough said tube, a helically coiled bimetallic element connected atone end to said shaft and at its other end to said tube, a member fixedto the tube and having bearing engagement with said support, said memberproviding a bearing for the adjacent end of the shaft, a spring actingbetween the support and the tube to hold said member in bearingengagement with the support, and a movable switch member mounted on theshaft adjacent said bearing.

7. A thermostat comprising, in combination, a support, an elongated tuberotatively mounted in 75 said support and projecting a substantialdistance to one side thereof, an arm rigid with one end of said tubeadjacent the opposite side of the support, a shaft journaled at one endin said arm and extending through said tube, a thermostatic element inthe form of a helically coiled bimetallic strip having one end securedto said tube and the other end secured to said shaft, spring meansacting upon said tube to hold the latter in position in the support, amanually operable adjusting lever connected with said arm to move it,and a control switch having a movable contact member mounted on saidshaft.

8. A control instrument of the character set forth comprising a shaft,means including a sensitive actuating element for imparting rotativemovement to the shaft in response to temperature changes, a pair ofstationary switch contacts spaced apart, a movable switch member havinga portion interposed between said contacts, and means normally carryingsaid switch member in a predetermined relation to said shaft including ablock fixed to said shaft, and a spring clamp adapted to yield in eitherdirection from said normal relation to permit rotation of the shaft ineither direction independently of the switch member and operable to movethe switch member only when it occupies a definite angular relation tosaid shaft.

9. An insertion thermostat comprising a casing to be supported in anormal upright position, temperature responsive switch actuating meansprojecting rearwardly of the casing, and means for supporting the casingin said upright position with the temperature responsive means insertedthrough the wall of a furnace or other structure, said supporting meanscomprising a threaded bushing adapted to be screwed into said structurewith the temperature responsive means passing through the bushing, and athreaded fastening member entered through said casing and anchored insaid bushing, said casing having an arcuate slot through which saidmember extends, and said bushing having a plurality of holes forreceiving said fastening member selectively depending upon the positionof the bushing when secured in said structure.

10. In an insertion thermostat, a base, a member rotatably mounted onsaid base, an arm rigid with said member, an adjusting lever pivoted onsaid base and having an engagement with said arm whereby to rotate saidmember, said lever having an enlarged portion formed withan arcuateslot, and means including a bolt projecting through said slot urgingsaid lever against said base to retain the lever in adjusted position.

11. A sensitive control instrument comprising, in combination, a controldevice having two stationary switch contacts and a movable contactinterposed between the stationary contacts, means for actuatingsaidcontrol device including a sensitive actuating element, and amotion-transmitting connection between the movable contact and saidactuating element including two members, one connected with theactuating element and the other connected to said movable contact, andspring means constantly acting to maintain said two members in apredetermined angular relation for motion transmitting purposes butadapted to yield to permit relative movement between them in eitherdirection, said spring means being operative to transmit movement tosaid movable contact only when said two members have been restored tosaid predetermined angular'relation.

12. A control instrument having, in combination, a sensitive actuatingelement having a normal range of operation, a pair of opposed closelyspaced contacts, a movable contact disposed between said stationarycontacts and having a limited normal range of movement determined by thespacing of said stationary contacts in the normal range of operation ofsaid actuating element, and a motion-transmitt ng device operative tocause said movable contact to move with said actuating element inopposite directions; said device comprising relatively movable partsinterposed between the actuating element and said movable contact andoperative to permit movements of said actuating element beyond itsnormal range in either direction, and spring means acting to hold saidparts against relative movement in either direction from a predeterminednormal relation and coacting therewith to cause said movable contact tomove with said actuating element only when said parts occupy saidpredetermined normal relation.

13. A control instrument having, in combina-' tion, a sensitiveactuating element having a normal range of operation, a pair of opposedclosely spaced contacts, a movable contact disposed between saidstationary contacts and having a limited normal range of movementdetermined by the spacing of said stationary contacts in the normalrange of operation of said actuating element, and a motion-transmittingdevice operative to cause said movable contact to move with saidactuating element only in the normal range of operation of saidactuating element, said clevice comprising relatively movableparts'respectively connected with the actuating element and the movablecontact and having coacting positioning surfaces to establish a normalpredetermined relation between the parts, and spring means cooperatingwith said surfaces to hold said parts yieldably against relativemovement in either direction from said normal relation, said springmeans being operative as an incident to the movement of said actuatingelement beyond its normal range of operation in either direction topermit relative movement between said parts in either direction and tore-establish said normal relation between the parts as an incident tothe reverse movement of the actuating element into its said normal rangeof operation.

14. A control instrument comprising, in combination, a shaft, athermostatic element arranged to turn the shaft in opposite directionsin response to temperature changes, a movable contact arm supported fromsaid shaft, a pair of opposed normally stationary contacts between whichsaid arm is movable and defining a limited range of movement of saidarm, and means cooperating with said shaft and arm and coupling the armto move with the shaft through certain phases only of the movement ofthe shaft corresponding to said limited range of movement of the arm,said means including a member rigid with the shaft, a second membermovable with said arm, said members having cooperating surfaces normallyengageable with each other to determine a definite angular relationbetween said arm and said shaft during the movement of said arm betweensaid contacts, but adapted for relative movement in opposite directionsas an incident to continued rotational movement of the shaft in oppositedirections after engagement of said arm with the respective contacts,and a spring normally acting on one of the members to maintain saidpredetermined angular relation and yieldable upon engagement of said armwith either of said contacts to permit relative movement between saidmembers to be continued irrespective of the direction of movement of theshaft by said thermostatic element.

15. A control instrument having in combination a pair of fixed contactsspaced a short distance apart, a movable contact having a limited rangeof movement between said fixed contacts, a rotatable member, a sensitiveactuating element for imparting rotational movement to said memberhaving a normal range of operation proportional to the limited range ofmovement of the movable contact, and a yieldable motion transmittingconnection between said member and the movable contact operative toimpart movement to the movable contact only during said normal range ofoperation of the actuating element, said connection comprising two partsfixed to the rotatable member and the movable contact respectively, andspring means acting to hold said parts together with a yieldingpressure, said spring means acting on said parts to transmit movement tothe movable contact only during said normal range of operation of theactuating element and yieldable to permit relative movement between theparts upon movement of the actuating element beyond its normal range ofoperation in either direction.

16. A control instrument having, in combination, a pair of fixedcontacts spaced a short distance apart, amovable contact element havinga limited range of movement between said fixed contacts, sensitiveactuating means for imparting movement to said movable contact elementincluding an actuating member having a normal range of operationproportional to the limited range of movement of the movable contact,and a yieldable motion transmitting connection between said member andthe movable contact element, said connection comprising spring meansacting to transmit movement from said member to the movable contact onlyduring said normal operation of the actuating member, and saidconnection being yieldable upon the engagement of the movable contactwith either of said stationary contacts to permit movement of theactuating member beyond its normal range of operation in eitherdirection.

17. A control instrument having, in combination, a movable switch armhaving a limited normal range of movement, a thermal actuating elementhaving a normal range of operation proportional to the limited range ofmovement of said arm and an abnormal range of movement in response toextreme temperature changes substantially greater than said limitedmovement of the switch arm, and a motion transmitting connection betweensaid arm and said thermal element including a spring acting upon saidarm to effect the transmission of movement from the thermal element tothe arm only during said normal range of operation of the element, saidconnection being yieldable upon the interruption of the movement of theswitch arm in either direction to permit abnormal movement of theactuating clement beyond said normal range of operation thereof.

PRESTON W. CUMMINGS.

